Eight speed automatic transmission

ABSTRACT

An automatic transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may be either clutches or brakes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/909,087 filed on Mar. 30, 2007. The disclosure of the above application is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed automatic transmission having a plurality of planetary gear sets and a plurality of torque transmitting devices and more particularly to an eight speed automatic transmission having four planetary gear sets and a plurality of torque transmitting devices.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.

A typical multiple speed automatic transmission uses a combination of friction clutches, planetary gear arrangements and fixed interconnections to achieve a plurality of gear ratios. The number and physical arrangement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios.

While current automatic transmissions achieve their intended purpose, the need for new and improved transmission configurations which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness and improved packaging, primarily reduced size and weight, is essentially constant. Accordingly, there is a need for an improved, cost-effective, compact multiple speed automatic transmission.

SUMMARY

An automatic transmission is provided that includes an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may be either clutches or brakes.

One embodiment of the transmission includes an input member, an output member, and first, second, third and fourth planetary gear sets each having first, second and third members. A first interconnecting member continuously interconnects the first member of the first planetary gear set with a stationary member. A second interconnecting member continuously interconnects the second member of the first planetary gear set with the second member of the third planetary gear set. A third interconnecting member continuously interconnects the third member of the first planetary gear set with the second member of the second planetary gear set. A fourth interconnecting member continuously interconnects the first member of the second planetary gear set with the first member of the third planetary gear set. Five torque transmitting devices are selectively engageable to interconnect one of the first members, second members, and third members with at least one of the first members, second members, third members, and the stationary member. The torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

In one aspect of the present invention, a first of the five torque transmitting devices is selectively engageable to interconnect at least one of the first member of the fourth planetary gear set and the input member with at least one of the second member of the third planetary gear set and the second member of the first planetary gear set.

In another aspect of the present invention, a second of the five torque transmitting devices is selectively engageable to interconnect the third member of the second planetary gear set with the third member of the fourth planetary gear set.

In yet another aspect of the present invention, a third of the five torque transmitting devices is selectively engageable to interconnect the third member of the fourth planetary gear set with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set.

In yet another aspect of the present invention, a fourth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set.

In yet another aspect of the present invention, a fifth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear set with at least one of the first member of the first planetary gear set and the stationary member.

In yet another aspect of the present invention, a first of the five torque transmitting devices is selectively engageable to interconnect at least one of the first member of the fourth planetary gear set and the input member with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set.

In yet another aspect of the present invention, a second of the five torque transmitting devices is selectively engageable to interconnect the third member of the third planetary gear set with the third member of the fourth planetary gear set.

In yet another aspect of the present invention, a third of the five torque transmitting devices is selectively engageable to interconnect the third member of the fourth planetary gear set with the third member of the second planetary gear set.

In yet another aspect of the present invention, a fourth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear with the third member of the second planetary gear set.

In yet another aspect of the present invention, a fifth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear set with the stationary member.

In yet another aspect of the present invention, the first members are sun gears, the second members are carrier members, and the third members are ring gears.

In yet another aspect of the present invention, the first member of the first planetary gear set is a ring gear, the second member of the first planetary gear set is a sun gear, the third member of the first planetary gear set is a carrier member, the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a ring gear, the third member of the second planetary gear set is a sun gear, the first member of the third planetary gear set is a ring gear, the second member of the third planetary gear set is a sun gear, the third member of the third planetary gear set is a carrier member, the first member of the fourth planetary gear set is a sun gear, the second member of the fourth planetary gear set is a carrier member, and the third member of the fourth planetary gear set is a ring gear.

In yet another aspect of the present invention, the input member is continuously interconnected with the first member of the fourth planetary gear set and the output member is continuously interconnected with the third member of the third planetary gear set.

In yet another aspect of the present invention, the input member is continuously interconnected with the first member of the fourth planetary gear set and the output member is continuously interconnected with at least one of the third member of the first planetary gear set and the second member of the second planetary gear set.

In yet another aspect of the present invention, the stationary member is a transmission housing.

Another embodiment of the transmission of the present invention includes an input member, an output member, first, second, third and fourth planetary gear sets each having a sun gear, a carrier member, and a ring gear, wherein the input member is continuously interconnected with the sun gear of the fourth planetary gear set and the output member is continuously interconnected with the ring gear of the third planetary gear set. A first interconnecting member continuously interconnects the sun gear of the first planetary gear set with a stationary member. A second interconnecting member continuously interconnects the carrier member of the first planetary gear set with the carrier member of the third planetary gear set. A third interconnecting member continuously interconnects the ring gear of the first planetary gear set with the carrier member of the second planetary gear set. A fourth interconnecting member continuously interconnects the sun gear of the second planetary gear set with the sun gear of the third planetary gear set. A first torque transmitting device is selectively engageable to interconnect at least one of the sun gear of the fourth planetary gear set and the input member with at least one of the carrier member of the third planetary gear set and the carrier member of the first planetary gear set. A second torque transmitting device is selectively engageable to interconnect the ring gear of the second planetary gear set with the ring gear of the fourth planetary gear set. A third torque transmitting device is selectively engageable to interconnect the ring gear of the fourth planetary gear set with at least one of the sun gear of the second planetary gear set and the sun gear of the third planetary gear set. A fourth torque transmitting device is selectively engageable to interconnect the carrier member of the fourth planetary gear with at least one of the sun gear of the second planetary gear set and the sun gear of the third planetary gear set. A fifth torque transmitting device is selectively engageable to interconnect the carrier member of the fourth planetary gear set with at least one of the sun gear of the first planetary gear set and the stationary member. The torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

Yet another embodiment of the transmission of the present invention includes an input member, an output member, first, second, third and fourth planetary gear sets each having a sun gear, a carrier member, and a ring gear, wherein the input member is continuously interconnected with the sun gear of the fourth planetary gear set and the output member is continuously interconnected with at least one of the carrier member of the first planetary gear set and the ring gear of the second planetary gear set. A first interconnecting member continuously interconnects the ring gear of the first planetary gear set with a stationary member. A second interconnecting member continuously interconnects the sun gear of the first planetary gear set with the sun gear of the third planetary gear set. A third interconnecting member continuously interconnects the carrier member of the first planetary gear set with the ring gear of the second planetary gear set. A fourth interconnecting member continuously interconnects the carrier member of the second planetary gear set with the ring gear of the third planetary gear set. A first torque transmitting device is selectively engageable to interconnect at least one of the sun gear of the fourth planetary gear set and the input member with at least one of the carrier member of the second planetary gear set and the ring gear of the third planetary gear set. A second torque transmitting device is selectively engageable to interconnect the carrier member of the third planetary gear set with the ring gear of the fourth planetary gear set. A third torque transmitting device is selectively engageable to interconnect the ring gear of the fourth planetary gear set with the sun gear of the second planetary gear set. A fourth torque transmitting device is selectively engageable to interconnect the carrier member of the fourth planetary gear with the sun gear of the second planetary gear set. A fifth torque transmitting device is selectively engageable to interconnect the carrier member of the fourth planetary gear set with the stationary member. The torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

Further aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speed automatic transmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of the eight speed automatic transmission according to the present invention;

FIG. 3 is a truth table presenting the state of engagement of the various torque transmitting devices in each of the available forward and reverse speeds or gear ratios of the automatic transmission illustrated in FIGS. 1 and 2;

FIG. 4 is a lever diagram of another embodiment of an eight speed automatic transmission according to the present invention;

FIG. 5 is a diagrammatic view of another embodiment of the eight speed automatic transmission according to the present invention; and

FIG. 6 is a truth table presenting the state of engagement of the various torque transmitting devices in each of the available forward and reverse speeds or gear ratios of the automatic transmission illustrated in FIGS. 4 and 5.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular example provided, the eight speed automatic transmission of the present invention has an arrangement of permanent mechanical connections between the members of the four planetary gear sets. These permanent mechanical connections relate the transmission embodiments. More specifically, a first component or member of a first planetary gear set is permanently coupled to a ground, stationary member, or transmission housing. A second component or member of the first planetary gear set is permanently coupled to a second component or member of a third planetary gear set. A third component or member of the first planetary gear set is permanently coupled to a second component or member of a second planetary gear set. Finally, a first component or member of the second planetary gear set is permanently coupled to a first component or member of the third planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed automatic transmission 10 is illustrated in a lever diagram format. A lever diagram is a schematic representation of the components of a mechanical device such as an automatic transmission. Each individual lever represents a planetary gear set wherein the three basic mechanical components of the planetary gear are each represented by a node. Therefore, a single lever contains three nodes: one for the sun gear member, one for the planet gear carrier member, and one for the ring gear member. The relative length between the nodes of each lever can be used to represent the ring-to-sun ratio of each respective gearset. These lever ratios, in turn, are used to vary the gear ratios of the transmission in order to achieve an appropriate ratio and ratio progression. Mechanical couplings or interconnections between the nodes of the various planetary gear sets are illustrated by thin, horizontal lines and torque transmitting devices such as clutches and brakes are presented as interleaved fingers. If the device is a brake, one set of the fingers is grounded. Further explanation of the format, purpose and use of lever diagrams can be found in SAE Paper 810102, “The Lever Analogy: A New Tool in Transmission Analysis” by Benford and Leising, which is hereby fully incorporated by reference.

The automatic transmission 10 includes an input shaft or member 12, a first planetary gear set 14 having three nodes: a first node 14A, a second node 14B and a third node 14C, a second planetary gear set 16 having three nodes: a first node 16A, a second node 16B and a third node 16C, a third planetary gear set 18 having three nodes: a first node 18A, a second node 18B and a third node 18C, a fourth planetary gear set 20 having three nodes: a first node 20A, a second node 20B and a third node 20C, and an output shaft or member 22.

The first node 14A of the first planetary gear set 14 is coupled to a ground, stationary member, or transmission housing 40. The second node 14B of the first planetary gear set 14 is coupled to the second node 16B of the second planetary gear set 16. The third node 14C of the first planetary gear set 14 is coupled to the third node 18C of the third planetary gear set 18. The first node 16A of the second planetary gear set 16 is coupled to the first node 18A of the third planetary gear set 18. The input shaft or member 12 is coupled to the first node 20A of the fourth planetary gear set 20. The output shaft or member 22 is coupled to the second node 18B of the third planetary gear set 18.

A first clutch 26 selectively connects the first node 20A of the fourth planetary gear set 20 to the third node 14C of the first planetary gear set 14 and to the third node 18C of the third planetary gear set 18. A second clutch 28 selectively connects the third node 16C of the second planetary gear set 16 to the second node 20B of the fourth planetary gear set 20. A third clutch 30 selectively connects the first node 16A of the second planetary gear set 16 and the first node 18A of the third planetary gear set 18 to the second node 20B of the fourth planetary gear set 20. A fourth clutch 32 selectively connects the first node 16A of the second planetary gear set 16 and the first node 18A of the third planetary gear set 18 to the third node 20C of the fourth planetary gear set 20. Finally, a first brake 34 selectively connects the third node 20C of the fourth planetary gear set 20 to ground, stationary member, or transmission housing 40.

Referring now to FIG. 2, a stick diagram presents a schematic layout of the embodiment of the eight speed transmission 10 according to the present invention. In FIG. 2, the numbering from the lever diagram of FIG. 1 is carried over. The clutches, brakes and couplings are correspondingly presented whereas the nodes of the planetary gear sets now appear as components of planetary gear sets such a sun gear members, ring gear members, planet gears and planet gear carrier members.

For example, the first planetary gear set 14 includes a first sun gear member 14A, a first ring gear member 14B, and a first planet carrier member 14C that includes a plurality of planet gears 14D rotatably disposed thereon. The planet gears 14D are each intermeshed with both the first sun gear member 14A and the first ring gear member 14B. The second planetary gear set 16 includes a second sun gear member 16A, a second ring gear member 16C, and a second planet carrier member 16B that includes a plurality of planet gears 16D rotatably disposed thereon. The planet gears 16D are each intermeshed with both the second sun gear member 16A and the second ring gear member 16C. The third planetary gear set 18 includes a third sun gear member 18A, a third ring gear member 18B, and a third planet carrier member 18C that includes a plurality of planet gears 18D rotatably disposed thereon. The planet gears 18D are each intermeshed with both the third sun gear member 18A and the third ring gear member 18B. The fourth planetary gear set 20 includes a fourth sun gear member 20A, a fourth ring gear member 20B, and a fourth planet carrier member 20C that includes a first plurality of planet gears 20D and a second plurality of planet gears 20E rotatably disposed thereon. The planet gears 20D are each intermeshed with both the planet gears 20E and the fourth ring gear member 20B. The planet gears 20E are each intermeshed with both the planet gears 20D and the fourth sun gear member 20A.

The input shaft or member 12 is coupled to and directly drives the fourth sun gear member 20A and the first clutch 26. A first shaft or interconnecting member 42 interconnects the first sun gear member 14A and brake 34 to ground, stationary member, or transmission housing 40. A second shaft or interconnecting member 44 couples the first planet carrier member 14C to the third planet carrier member 18C. A third shaft or interconnecting member 46 couples the first ring gear member 14B to the second planet carrier member 16B. A fourth shaft or interconnecting member 48 interconnects the fourth ring gear member 20B, the third clutch 30, and the second clutch 28. A fifth shaft or interconnecting member 50 interconnects the fourth clutch 32 to the second sun gear member 16A. A sixth shaft or interconnecting member 52 interconnects the second sun gear member 16A to the third sun gear member 18A. A seventh shaft or interconnecting member 54 interconnects the first clutch 26 to the third planet carrier member 18C. An eighth shaft or interconnecting member 56 interconnects the fourth planet carrier member 20C to the brake 34. A ninth shaft or interconnecting member 58 interconnects the fourth planet carrier member 20C to the fourth clutch 32. A tenth shaft or interconnecting member 60 interconnects the second ring gear member 16C with the second clutch 28.

The first clutch 26 selectively couples the input shaft or member 12 and the fourth sun gear member 20A to the third planet carrier member 18C and the first planet carrier member 14C. The second clutch 28 selectively couples the fourth ring gear member 20B to the second ring gear member 16C. The third clutch 30 selectively couples the fourth ring gear member 20B to the third sun gear member 18A and the second sun gear member 16A. The fourth clutch 32 selectively couples the fourth planet carrier member 20C to the third sun gear member 18A and the second sun gear member 16A. The brake 34 selectively couples the fourth planet carrier member 20C to the first sun gear member 14A and to ground, stationary member, or transmission housing 40 in order to restrict rotation of the fourth planet carrier member 20C relative to the transmission housing 40. The output shaft or member 22 is coupled to the third ring gear member 18B.

Referring now to FIGS. 2 and 3, the operation of the embodiment of the eight speed automatic transmission 10 will be described. It will be appreciated that the automatic transmission 10 is capable of transmitting torque from the input shaft or member 12 to the output shaft or member 22 in eight forward speed or torque ratios and one reverse speed or torque ratio. Each forward and reverse speed or torque ratio is attained by engagement of one or more of the torque transmitting devices as will be explained below. FIG. 3 is a truth table presenting the various combinations of torque transmitting devices that are activated or engaged to achieve the various gear states. Actual numerical gear ratios of the various gear states are also presented although it should be appreciated that these numerical values are exemplary only and that they may be adjusted over significant ranges to accommodate various applications and operational criteria of the automatic transmission 10.

To establish gear ratios, three torque transmitting devices are engaged for each gear state. The engaged torque transmitting devices are represented by an “X” in each respective row. For example, to establish reverse gear, the brake 34, the first clutch 26, and the second clutch 28 are engaged or activated. The first brake 34 selectively couples the fourth planet carrier member 20C to the first sun gear member 14A and to ground, stationary member, or transmission housing 40 in order to restrict rotation of the fourth planet carrier member 20C relative to the transmission housing 40. The first clutch 26 selectively couples the input shaft 12 and the fourth sun gear member 20A to the third planet carrier member 18C, and the first planet carrier member 14C. The second clutch 28 selectively couples the fourth ring gear member 20B to the second ring gear member 16C. Likewise, the eight forward ratios are achieved through different combinations of clutch engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation and gear states of the eight speed automatic transmission 10 assumes, first of all, that all clutches and brakes not specifically referenced in a given gear state are inactive or disengaged and, second of all, that during gear member shifts, i.e., changes of gear state, between at least adjacent gear states, a clutch or brake engaged or activated in both gear states will remain engaged or activated.

Turning now to FIG. 4, a lever diagram for another embodiment of an eight speed automatic transmission 100 is illustrated. The automatic transmission 100 includes an input shaft or member 112, a first planetary gear set 114 having three nodes: a first node 114A, a second node 114B and a third node 114C, a second planetary gear set 116 having three nodes: a first node 116A, a second node 116B and a third node 116C, a third planetary gear set 118 having three nodes: a first node 118A, a second node 118B and a third node 118C, a fourth planetary gear set 120 having three nodes: a first node 120A, a second node 120B and a third node 120C, and an output shaft or member 122.

The first node 114A of the first planetary gear set 114 is coupled to a ground, stationary member, or transmission housing 140. The second node 114B of the first planetary gear set 114 is coupled to the second node 116B of the second planetary gear set 116. The third node 114C of the first planetary gear set 114 is coupled to the third node 118C of the third planetary gear set 118. The first node 116A of the second planetary gear set 116 is coupled to the first node 118A of the third planetary gear set 118. The input shaft 112 is coupled to first node 120A of the fourth planetary gear set 120. The output shaft 122 is coupled to the second node 114B of the first planetary gear set 114.

A first clutch 126 selectively connects the first node 120A of the fourth planetary gear set 120 to the first node 118A of the third planetary gear set 118 and to the first node 116A of the second planetary gear set 116. A second clutch 128 selectively connects the second node 120B of the fourth planetary gear set 120 to the second node 118B of the third planetary gear set 118. A third clutch 130 selectively connects the third node 116C of the second planetary gear set 116 to the second node 120B of the fourth planetary gear set 120. A fourth clutch 132 selectively connects the third node 116C of the second planetary gear set 116 to the third node 120C of the fourth planetary gear set 120. Finally, a brake 134 selectively connects the third node 120C of the fourth planetary gear set 120 to ground, stationary member, or transmission housing 140.

Referring now to FIG. 5, a stick diagram presents a schematic layout of the embodiment of the eight speed transmission 100 according to the present invention. In FIG. 5, the numbering from the lever diagram of FIG. 4 is carried over. The clutches, brakes and couplings are correspondingly presented whereas the nodes of the planetary gear sets now appear as components of planetary gear sets such a sun gear members, ring gear members, planet gears and planet gear carrier members.

For example, the first planetary gear set 114 includes a first sun gear member 114C, a first ring gear member 114A, and a first planet carrier member 114B that includes a plurality of planet gears 114D rotatably disposed thereon. The planet gears 114D are each intermeshed with both the first sun gear member 114C and the first ring gear member 114A. The second planetary gear set 116 includes a second sun gear member 116C, a second ring gear member 116B, and a second planet carrier member 116A that includes a plurality of planet gears 116D rotatably disposed thereon. The planet gears 116D are each intermeshed with both the second sun gear member 116C and the second ring gear member 116B. The third planetary gear set 118 includes a third sun gear member 118C, a third ring gear member 118A, and a third planet carrier member 118B that includes a plurality of planet gears 118D rotatably disposed thereon. The planet gears 118D are each intermeshed with both the third sun gear member 118C and the third ring gear member 118A. The fourth planetary gear set 120 includes a fourth sun gear member 120A, a fourth ring gear member 120B, and a fourth planet carrier member 120C that includes a first plurality of planet gears 120D and a second plurality of planet gears 120E rotatably disposed thereon. The planet gears 120D are each intermeshed with both the planet gears 120E and the fourth ring gear member 120B. The planet gears 120E are each intermeshed with both the planet gears 120D and the fourth sun gear member 120A.

The input shaft 112 is coupled to and directly drives the fourth sun gear member 120A and interconnects with the first clutch 126. A first shaft or interconnecting member 142 interconnects the fourth planet carrier member 120C with brake 134. A second shaft or interconnecting member 144 interconnects the first sun gear member 114C with the third sun gear member 118C. A third shaft or interconnecting member 146 interconnects the first planet carrier member 114B with the second ring gear member 116B and the output shaft or member 122. A fourth shaft or interconnecting member 148 interconnects the third clutch 130 and the fourth clutch 132 with the second sun gear member 116C. A fifth shaft or interconnecting member 150 interconnects the fourth ring gear member 120B with the second clutch 128. A sixth shaft or interconnecting member 152 interconnects the second planet carrier member 116A with the third ring gear member 118A. A seventh shaft or interconnecting member 154 couples the first clutch 126 to the second planet carrier member 116A. An eighth shaft or interconnecting member 158 couples the first ring gear member 114A to ground, stationary member, or transmission housing 140 in order to restrict rotation of the first ring gear member 114A relative to the transmission housing 140. A ninth shaft or interconnecting member 160 interconnects the fourth ring gear member 120B with the third clutch 130. A tenth shaft or interconnecting member 162 interconnects the fourth planet carrier member 120C with the fourth clutch 132. An eleventh shaft or interconnecting member 164 interconnects the third planet carrier member 118B with the second clutch 128.

The first clutch 126 selectively couples the input shaft 112 and the fourth sun gear member 120A to the second planet carrier member 116A. The second clutch 128 selectively couples the third planet carrier member 118B to the fourth ring gear member 120B. The third clutch 130 selectively couples the fourth ring gear member 120B to the second sun gear member 116C. The fourth clutch 132 selectively couples the fourth planet carrier member 120C to the second sun gear member 116C. The brake 134 selectively couples the fourth planet carrier member 120C to ground, stationary member, or transmission housing 140 in order to restrict rotation of the fourth planet carrier member 120C relative to the transmission housing 140. The output shaft 122 is coupled to the second ring gear member 116B and the first planet carrier member 114B via the third interconnecting member 146.

Referring now to FIGS. 5 and 6, the operation of the embodiment of the eight speed automatic transmission 100 will be described. It will be appreciated that the automatic transmission 100 is capable of transmitting torque from the input shaft or member 112 to the output shaft or member 122 in eight forward speed or torque ratios and one reverse speed or torque ratio. Each forward and reverse speed or torque ratio is attained by engagement of one or more of the torque transmitting devices as will be explained below. FIG. 6 is a truth table presenting the various combinations of torque transmitting devices that are activated or engaged to achieve the various gear states. Actual numerical gear ratios of the various gear states are also presented although it should be appreciated that these numerical values are exemplary only and that they may be adjusted over significant ranges to accommodate various applications and operational criteria of the automatic transmission 100.

To establish gear ratios, three torque transmitting devices are engaged for each gear state. The engaged torque transmitting devices are represented by an “X” in each respective row. For example, to establish reverse gear, the brake 134, the first clutch 126, and the second clutch 128 are engaged or activated. The brake 134 selectively couples the fourth planet carrier member 120C to ground, stationary member, or transmission housing 140 in order to restrict rotation of the fourth planet carrier member 120C relative to the transmission housing 140. The first clutch 126 selectively couples the input shaft 112 and the fourth sun gear member 120A to the second planet carrier member 116A. The second clutch 128 selectively couples the third planet carrier member 118B to the fourth ring gear member 120B. Likewise, the eight forward ratios are achieved through different combinations of clutch engagement, as shown in FIG. 6.

It will be appreciated that the foregoing explanation of operation and gear states of the eight speed automatic transmission 100 assumes, first of all, that all clutches and brakes not specifically referenced in a given gear state are inactive or disengaged and, second of all, that during gear member shifts, i.e., changes of gear state, between at least adjacent gear states, a clutch or brake engaged or activated in both gear states will remain engaged or activated.

The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having first, second and third members; a first interconnecting member continuously interconnecting the first member of the first planetary gear set with a stationary member; a second interconnecting member continuously interconnecting the second member of the first planetary gear set with the second member of the third planetary gear set; a third interconnecting member continuously interconnecting the third member of the first planetary gear set with the second member of the second planetary gear set; a fourth interconnecting member continuously interconnecting the first member of the second planetary gear set with the first member of the third planetary gear set; and five torque transmitting devices selectively engageable to interconnect one of the first members, second members, and third members with at least one of the first members, second members, third members, and the stationary member; and wherein the torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 2. The transmission of claim 1 wherein a first of the five torque transmitting devices is selectively engageable to interconnect at least one of the first member of the fourth planetary gear set and the input member with at least one of the second member of the third planetary gear set and the second member of the first planetary gear set.
 3. The transmission of claim 2 wherein a second of the five torque transmitting devices is selectively engageable to interconnect the third member of the second planetary gear set with the third member of the fourth planetary gear set.
 4. The transmission of claim 3 wherein a third of the five torque transmitting devices is selectively engageable to interconnect the third member of the fourth planetary gear set with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set.
 5. The transmission of claim 4 wherein a fourth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set.
 6. The transmission of claim 5 wherein a fifth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear set with at least one of the first member of the first planetary gear set and the stationary member.
 7. The transmission of claim 1 wherein a first of the five torque transmitting devices is selectively engageable to interconnect at least one of the first member of the fourth planetary gear set and the input member with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set.
 8. The transmission of claim 7 wherein a second of the five torque transmitting devices is selectively engageable to interconnect the third member of the third planetary gear set with the third member of the fourth planetary gear set.
 9. The transmission of claim 8 wherein a third of the five torque transmitting devices is selectively engageable to interconnect the third member of the fourth planetary gear set with the third member of the second planetary gear set.
 10. The transmission of claim 9 wherein a fourth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear with the third member of the second planetary gear set.
 11. The transmission of claim 10 wherein a fifth of the five torque transmitting devices is selectively engageable to interconnect the second member of the fourth planetary gear set with the stationary member.
 12. The transmission of claim 1 wherein the first members are sun gears, the second members are carrier members, and the third members are ring gears.
 13. The transmission of claim 1 wherein the first member of the first planetary gear set is a ring gear, the second member of the first planetary gear set is a sun gear, the third member of the first planetary gear set is a carrier member, the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a ring gear, the third member of the second planetary gear set is a sun gear, the first member of the third planetary gear set is a ring gear, the second member of the third planetary gear set is a sun gear, the third member of the third planetary gear set is a carrier member, the first member of the fourth planetary gear set is a sun gear, the second member of the fourth planetary gear set is a carrier member, and the third member of the fourth planetary gear set is a ring gear.
 14. The transmission of claim 1 wherein the input member is continuously interconnected with the first member of the fourth planetary gear set and the output member is continuously interconnected with the third member of the third planetary gear set.
 15. The transmission of claim 1 wherein the input member is continuously interconnected with the first member of the fourth planetary gear set and the output member is continuously interconnected with at least one of the third member of the first planetary gear set and the second member of the second planetary gear set.
 16. The transmission of claim 1 wherein the stationary member is a transmission housing.
 17. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having first, second and third members, wherein the input member is continuously interconnected with the first member of the fourth planetary gear set and the output member is continuously interconnected with the third member of the third planetary gear set; a first interconnecting member continuously interconnecting the first member of the first planetary gear set with a stationary member; a second interconnecting member continuously interconnecting the second member of the first planetary gear set with the second member of the third planetary gear set; a third interconnecting member continuously interconnecting the third member of the first planetary gear set with the second member of the second planetary gear set; a fourth interconnecting member continuously interconnecting the first member of the second planetary gear set with the first member of the third planetary gear set; a first torque transmitting device selectively engageable to interconnect at least one of the first member of the fourth planetary gear set and the input member with at least one of the second member of the third planetary gear set and the second member of the first planetary gear set; a second torque transmitting device selectively engageable to interconnect the third member of the second planetary gear set with the third member of the fourth planetary gear set; a third torque transmitting device selectively engageable to interconnect the third member of the fourth planetary gear set with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set; a fourth torque transmitting device selectively engageable to interconnect the second member of the fourth planetary gear with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set; and a fifth torque transmitting device selectively engageable to interconnect the second member of the fourth planetary gear set with at least one of the first member of the first planetary gear set and the stationary member, and wherein the torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 18. The transmission of claim 17 wherein the first members are sun gears, the second members are carrier members, and the third members are ring gears.
 19. The transmission of claim 17 wherein the stationary member is a transmission housing.
 20. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having first, second and third members, wherein the input member is continuously interconnected with the first member of the fourth planetary gear set and the output member is continuously interconnected with at least one of the third member of the first planetary gear set and the second member of the second planetary gear set; a first interconnecting member continuously interconnecting the first member of the first planetary gear set with a stationary member; a second interconnecting member continuously interconnecting the second member of the first planetary gear set with the second member of the third planetary gear set; a third interconnecting member continuously interconnecting the third member of the first planetary gear set with the second member of the second planetary gear set; a fourth interconnecting member continuously interconnecting the first member of the second planetary gear set with the first member of the third planetary gear set; a first torque transmitting device selectively engageable to interconnect at least one of the first member of the fourth planetary gear set and the input member with at least one of the first member of the second planetary gear set and the first member of the third planetary gear set; a second torque transmitting device selectively engageable to interconnect the third member of the third planetary gear set with the third member of the fourth planetary gear set; a third torque transmitting device selectively engageable to interconnect the third member of the fourth planetary gear set with the third member of the second planetary gear set; a fourth torque transmitting device selectively engageable to interconnect the second member of the fourth planetary gear with the third member of the second planetary gear set; and a fifth torque transmitting device selectively engageable to interconnect the second member of the fourth planetary gear set with the stationary member, and wherein the torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 21. The transmission of claim 20 wherein the first member of the first planetary gear set is a ring gear, the second member of the first planetary gear set is a sun gear, the third member of the first planetary gear set is a carrier member, the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a ring gear, the third member of the second planetary gear set is a sun gear, the first member of the third planetary gear set is a ring gear, the second member of the third planetary gear set is a sun gear, the third member of the third planetary gear set is a carrier member, the first member of the fourth planetary gear set is a sun gear, the second member of the fourth planetary gear set is a carrier member, and the third member of the fourth planetary gear set is a ring gear.
 22. The transmission of claim 20 wherein the stationary member is a transmission housing.
 23. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having a sun gear, a carrier member, and a ring gear, wherein the input member is continuously interconnected with the sun gear of the fourth planetary gear set and the output member is continuously interconnected with the ring gear of the third planetary gear set; a first interconnecting member continuously interconnecting the sun gear of the first planetary gear set with a stationary member; a second interconnecting member continuously interconnecting the carrier member of the first planetary gear set with the carrier member of the third planetary gear set; a third interconnecting member continuously interconnecting the ring gear of the first planetary gear set with the carrier member of the second planetary gear set; a fourth interconnecting member continuously interconnecting the sun gear of the second planetary gear set with the sun gear of the third planetary gear set; a first torque transmitting device selectively engageable to interconnect at least one of the sun gear of the fourth planetary gear set and the input member with at least one of the carrier member of the third planetary gear set and the carrier member of the first planetary gear set; a second torque transmitting device selectively engageable to interconnect the ring gear of the second planetary gear set with the ring gear of the fourth planetary gear set; a third torque transmitting device selectively engageable to interconnect the ring gear of the fourth planetary gear set with at least one of the sun gear of the second planetary gear set and the sun gear of the third planetary gear set; a fourth torque transmitting device selectively engageable to interconnect the carrier member of the fourth planetary gear with at least one of the sun gear of the second planetary gear set and the sun gear of the third planetary gear set; and a fifth torque transmitting device selectively engageable to interconnect the carrier member of the fourth planetary gear set with at least one of the sun gear of the first planetary gear set and the stationary member, and wherein the torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 24. A transmission comprising: an input member; an output member; first, second, third and fourth planetary gear sets each having a sun gear, a carrier member, and a ring gear, wherein the input member is continuously interconnected with the sun gear of the fourth planetary gear set and the output member is continuously interconnected with at least one of the carrier member of the first planetary gear set and the ring gear of the second planetary gear set; a first interconnecting member continuously interconnecting the ring gear of the first planetary gear set with a stationary member; a second interconnecting member continuously interconnecting the sun gear of the first planetary gear set with the sun gear of the third planetary gear set; a third interconnecting member continuously interconnecting the carrier member of the first planetary gear set with the ring gear of the second planetary gear set; a fourth interconnecting member continuously interconnecting the carrier member of the second planetary gear set with the ring gear of the third planetary gear set; a first torque transmitting device selectively engageable to interconnect at least one of the sun gear of the fourth planetary gear set and the input member with at least one of the carrier member of the second planetary gear set and the ring gear of the third planetary gear set; a second torque transmitting device selectively engageable to interconnect the carrier member of the third planetary gear set with the ring gear of the fourth planetary gear set; a third torque transmitting device selectively engageable to interconnect the ring gear of the fourth planetary gear set with the sun gear of the second planetary gear set; a fourth torque transmitting device selectively engageable to interconnect the carrier member of the fourth planetary gear with the sun gear of the second planetary gear set; and a fifth torque transmitting device selectively engageable to interconnect the carrier member of the fourth planetary gear set with the stationary member, and wherein the torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member. 